A chemical mechanical polishing is now widely used in order to remove a metal film, an insulating film, or a semiconductor film, thereby to form a wiring pattern or a planarized surface in fabrication of semiconductor devices or other electric devices.
Generally, a chemical mechanical polishing is carried out using a chemical mechanical polishing apparatus provided with a platen that holds a polishing pad and is rotatable at a predetermined rotational speed. Slurry is applied to the platen. An object to be polished (referred to as a wafer, hereinafter) such as a semiconductor wafer is held on a polishing head, rotated at a predetermined rotational speed, and is pressed at a predetermined pressure onto the polishing pad that is rotating along with the platen. In such a manner, the wafer is polished due to a mechanical and chemical polishing effect of the slurry. In the chemical mechanical polishing for the semiconductor device, a bubble resin film or a bubble-less resin film, which may have various degrees of hardness, is used as the polishing pad. As the slurry, a dispersive liquid may be used that is formed of abrasive grains including particles formed of, for example, silica (SiO2), alumina (Al2O3), and cerium dioxide (ceria, CeO2), water, and a solvent whose pH is adjusted, depending on a type of wafer. The slurry is dispensed at a predetermined rate onto the polishing pad during polishing.
In such a chemical mechanical polishing apparatus, a surface of the polishing pad is scraped in advance in many cased, thereby obtaining a rough surface, in order for the slurry to be retained on the polishing pad. Such scraping is called “dressing” or “conditioning”. The dressing is carried out by using a rotatable conditioning disk where diamond abrasive grains are buried. Specifically, the conditioning disk is rotated at a predetermined rotational speed and pressed at a predetermined pressure onto the polishing pad on the platen that is rotated at a predetermined rotational speed, so that the surface of the polishing pad is scraped by the diamond abrasive grains.
The slurry (the particles, water, and the solvent) can be stably retained on the rough surface of the polishing pad so scraped, and applied to the surface of the wafer to be polished. In addition, the rough surface of the polishing pad can retain polishing residues that are caused by polishing the surface of the wafer, so that scratches are prevented from being caused on the polished surface. The surface of the polishing pad is scraped by the conditioning disk thereby restoring the rough surface every time after one or several wafer(s) is polished.
Because such dressing needs to be carried with respect to an entire surface of the polishing pad, the conditioning disk is usually arranged near the platen and provided at a distal end of an arm that is pivotably supported by a bearing, so that the dressing is applied to the entire surface of the polishing pad by rotating the arm around the bearing.
Incidentally, when the chemical mechanical polishing is carried out for a relatively long period of time with respect to lots of wafers in the chemical mechanical polishing apparatus, the bearing of the arm may be worn off, which causes unwanted vibrations of the arm when the arm rotates. Once such vibrations take place, it becomes difficult to press the conditioning disk onto the polishing pad at a predetermined pressure, so that the dressing of the polishing pad cannot be desirably carried out.
When a reduction of the polishing speed is decreased or the scratches are caused, such problems are solved by changing the polishing pads and/or the slurries, however, the vibration-related problem cannot be solved in the same manner.